This invention relates to an electronic flash device and more particularly to a flash device which produces a flash by impressing a charge of a capacitor across a flash tube.
In devices of this type, the voltage of a DC power source such as a battery or the like is applied to a DC-DC converter, for example, through a two-position power source switch. The voltage is thus converted into a predetermined high DC voltage by the DC-DC converter. A capacitor is charged with this high DC voltage. The charge voltage of the capacitor is impressed on a flash tube to produce a flash of light. The DC-DC converter is controlled on the basis of the charge voltage of the capacitor in such a way as to make the high DC voltage which is obtained as the output of the converter approximately constant. In the conventional device, however, the energy of the battery is consumed rapidly because the DC-DC converter is incessantly in operation. In another type of conventional device, A DC-DC converter which is composed of devices such as a transistor oscillator, etc. is arranged to stop oscillating in response to lighting of a display device arranged to indicate the charge state of the capacitor. The oscillation of the converter is arranged to resume when the charge voltage of the capacitor becomes lower than a value at which the display device lights up and when the light of the display device is thus extinguished. Power consumption can be lowered by this arrangement. However, in cases where a discharge tube such as a neon tube is employed as the display device, there is a difference between the lighting voltage and the extinguishing voltage. Then, this voltage difference causes a variation in the amount of light to be emitted by a flash tube. With conventional devices of this type it is hardly possible to carry out a satisfactory photographic operation.